Sample Quiz 1 Questions

For the quiz, you may bring the class notes, the papers that were assigned, your writing assignments, the presentation you prepared, and the text book (assuming it arrives...)

In Ethernet: Distributed Packet Switching for Local Computer Networks, the author describes a link-layer protocol used to send packets around a local computer network. The physical medium for this network is a coax cable (like the kind you get cable TV from). The communicating computers are connected to the same cable at the same time.

Q1: When two computers try to inject a message into the cable at the same time, the messages collide. What does the Ethernet Protocol say the computers should do to try to get their respective packets out?

Q2: You are getting bad performance on your local Ethernet network. A little investigation shows that your nemesis, Net Vader, is watching lots of videos - and he's sharing the same Ethernet cable as you! To retaliate, you decide to create a rogue Ethernet card that gives preference to your packets over NV's during a collision. What will your card do different when a collision is detected? Be concrete.

Q3: The paper describes the use of a packet transceiver for connecting two coax cables into what looks like a single cable. Describe how such a system should handle collisions. (Hint: Consider two cases: A collision on one cable but not the other, a collision on both cables at the same time)

Q4: Do you think the tranceiver setup described in Q3 would scale out to hundreds of cable segments connected together? Briefly describe why you think it would or would not.

In Disk System Architectures for High-Performance Computing, you learned about the 5 RAID levels. Suppose you are configuring a service like photo.net with three RAIDs. In the questions below, make sure you explain your choice and list the key assumptions you used to choose the RAID you think is most appropriate.

Q5: You must first configure a RAID for photo.net's swap file. Given your knowledge of virtual memory, what RAID level is most appropriate? (assume photo.net has enough main memory to prevent thrashing)

Q6 Now, you must configure a RAID for photo.net's JPG files. These are the photo files that Philip or users upload. Assume there are 50,000 JPG files on photo.net and that 250 jpg files are uploaded each day. Also assume that photo.net must serve several requests for distinct JPG files at any one time, all day long. What RAID level is most appropriate?

Q7 Finally, you must configure the RAID for the Oracle database files. Like the JPG case, there are many more reads than writes. Unlike the JPG case, Oracle uses only a handful of very large files. Most of the time, the same file is being read or written. What RAID level is most appropriate?